The veteran defender, who helped France reach the 2006 World Cup final, was officially unveiled by the Glory on Monday and he is looking forward to training with his new team-mates on Tuesday.
However the 36-year-old does not yet know if he will be able to make his bow in Saturday's clash with Adelaide United having not played a competitive match in months after leaving former club Tottenham at the end of the last Barclays Premier League season.
Gallas, who will become the first Frenchman to play in the A-League, said at a press conference: "We will see if I can play or not.
"I didn't play for three months so I think we have to be careful - maybe don't take a risk.
"But we will see. I am very excited tomorrow (Tuesday) to train with my new team-mates and we will see."
Once he does start to play, the former Chelsea and Arsenal man has set his sights on helping Perth win some silverware.
"I have a new challenge - to win a trophy with Perth Glory," Gallas said.
"I think everybody knows that I am a player who likes to win."
After an encouraging start to the new season which has seen Perth claim eight points from their opening five matches, Glory coach Alistair Edwards could not hide his excitement at adding Gallas to his squad.
He also believes the signing reflects well on the A-League.
"It's a wonderful signing for the A-League," Edwards said.
"It shows how big the A-League has become, to attract world-class players like William to the competition.
"The Western Australian community is really excited, as I am. The playing group also is, and also the coaching staff."